public class Recusion {public int f(int n){if(n == 20){return 1;}else if(n == 21){return 4;}else{return f(n + 2) - 2 * f(n + 1);}}public int func(int n){if(n == 0){return 1;}else if(n == 1){return 4;}else{return func(n+2) - 2* func(n+1);}} }
